1. Field of the Invention
The present invention relates to battery mounting contacts. More particularly, the present invention relates to thin profile battery contacts for active tags used in active radio frequency identification and methods of producing the same.
2. State of the Art
Identification and tracking of objects are important concerns for most business operations. Presently, a leading method of object identification is bar code reading. Multiple objects can be identified by checking each object individually using a bar code reader which reads a bar code attached to each object. Although using bar codes on objects is a great advancement over manually and individually identifying objects, the bar code reading process is still time consuming and is also subject to bar code damage and bar code reader error. Furthermore, bar code readers usually require human operation wherein a person passes the bar code affixed to the object over the bar code reader, or passes the bar code reader over the bar code. Such human operation also introduces human error into the bar code reading process.
With such problems in bar code reading for identification, radio frequency identification (hereinafter "RF-ID") is rapidly becoming an important object identification method. The most important component of an RF-ID system is an information carrying tag which is affixed to the object. The information carrying tag functions in response to a coded radio frequency (hereinafter "RF") signal which the tag receives from a base station. In a passive information carrying tag, the tag receives its energy from the base station RF signal and reflects an RF carrier signal back to the base station. An active information carrying tag (hereinafter "active tag") contains a battery. The battery allows the active tag to retain, modify, and send information contained on the information carrying tag in response to the base station RF signal.
The active tag generally consists of a semiconductor chip having RF circuits, logic circuits, and memory. The active tag also has an antenna, a battery, a substrate for mounting the components, interconnections between components, and a physical enclosure, such as a plastic encasement or lamination.
In a typical configuration, the base station has a computer section which issues commands to an RF transmitter and receives commands from the RF receiver. The base station antenna sends RF signals to and receives RF signals from one or more active tags within the RF signal range, generally about 50 feet.
These active tags can be attached to articles of varying shapes and sizes and can be used in applications such as merchandise identification, item delivery control (letters and packages), inventory control and tracking, container control and tracking, surveillance, telemetry, automatic toll collection, and monitoring the location of vehicles and personnel.
As previously discussed, active tags require a battery. The functional specifications of the battery include a nominal cell voltage (typically 3 volts), high energy density and specific energy. Such specifications generally exist in lithium batteries. Furthermore, the battery must have a very thin profile in order to manufacture active tags which are unobtrusive and/or which can be used with a credit or debit card.
FIG. 8 illustrates a typical surface mount battery contact configuration 300. A battery 302, having a first contact surface 304 and a second contact surface 306, is positioned to contact the battery second contact surface 306 with a second contact 312 which is mounted on a substrate 310. A first contact 308 contacts the battery first contact surface 304. The first contact 308 typically has a battery contact portion 314 which extends over the battery 302 to contact the battery first contact surface 304, and a battery attachment portion 316 which is attached to the substrate 310. The battery first contact surface 304 may be an anode and the battery second contact surface 306 may be a cathode, or vice versa. The first contact 308 and the second contact 312 have conductive traces or the like (not shown) electrically connecting the first and second contacts 308, 312 to other active tag components (not shown). Although this surface mount battery contact configuration 300 is useful for some semiconductor applications or the like, it is not conducive to most active tag applications. The combined height of the substrate 310, the first contact 308, the battery 302, and the second contact 312 is too thick for most active tag applications.
U.S. Pat. No. 5,558,957 issued Sep. 24, 1996 to Datta et al. teaches a method for making a thin flexible battery for microelectronics applications. However, a flexible battery requires specialized manufacturing techniques, which would increase the cost of the active tags.
Therefore, it would be advantageous to develop an apparatus for mounting a commercially-available, inexpensive, thin lithium battery on a substrate while achieving a thin overall active tag profile without requiring complex processing steps or expensive components.